#include <iostream>
#include <string.h>
using namespace std;
int main() {
  char s1[25], s2[25];
  cin >> s1 >> s2;
  if (strstr(s2, s1)) {
    cout << s1 << " is substring of " << s2 << endl;
  } else if (strstr(s1, s2)) {
    cout << s2 << " is substring of " << s1 << endl;
  } else {
    cout << "No substring" << endl;
  }
}